Construction has started on the Roche Bros. supermarket in the former Filene’s building in Boston’s Downtown Crossing, according to developer Millennium Partners, which also released the first renderings of the store.

The Wellesley-based grocery chain is building a 25,000-square-foot store as part of the $689 million Millennium Tower/Burnham building project. The store will include 3,000 square feet of street-level retail and 22,000 square feet in the space formerly occupied by Filene’s Basement.

It’s slated to open in early 2015 with merchandise catering to downtown customers, from prepared food, flowers and artisan cheeses to household basics. Home delivery and catering also will be offered.

Roche Bros. also has an option to expand by about 10,000 square feet into the basement of the adjacent Millennium Tower.